This invention relates to a multi-wavelength demultiplexer, and, in particular, one that is an integrated, multi-layered structure especially suitable for fiber optical communication. Accordingly, it is a general object of this invention to provide new and improved devices of such character.
Communication through the utilization of optical fibers is well known. For example, techniques have been applied in optical communication in which light at one frequency is transmitted along an otpical fiber in one direction and light at a different frequency is transmitted along the same fiber in the opposite direction.
It is desirable, in order to increase the communication capability of an optical fiber, to transmit a plurality of signals at optical frequencies therealong, either in the same direction or in both directions. Hence, it is a purpose of this instant invention to provide a device that has the ability to demultiplex or to discriminate among the various frequencies transmitted simultaneously through an optical fiber.
A two-wavelength demultiplexing photodetector is discussed in the literature in "Improved Two-Wavelength Demultiplexing InGaAsP Photodetector" by J. C. Campbell et al., IEEE Journal of Quantum Electronics, Vol. QE-16, No. 6, June 1980, pp 601-603. Their method of detection of current response utilizes a p-n junction, whereby current flow is perpendicular to the various layers of there device. Their device is a two-wavelength demultiplexer.
In contradistinction to such a known structure, the instant invention utilizes contacts applied to the ends of various layers of a multilayered device. Hence, current flow is within the various layers, being confined by high band gap material (such as thin layers of aluminum arsenide). The instant invention has greater versatility in that more than two wavelengths can be multiplexed.